Nanoparticle Light Extraction Layer for OLED Contrast and Lifetime
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Solution Overview
Problem
OLED display panels face issues such as burn-in, short lifespan, and reduced contrast due to ambient light reflection, which is exacerbated when light extraction structures are combined with circular polarizers, leading to a loss in dark field effect.
Innovation Solution
Incorporating a light extraction layer with nanometer-sized particles above the top electrode in the display panel, where the particles have a diameter not exceeding 40 nm and a high refractive index, to enhance external quantum efficiency without compromising the dark field effect, thereby improving contrast and extending the panel's lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a circular polarizer is introduced to suppress ambient light reflection, then the contrast of the display panel is improved, but light loss increases by about half
Solution Approach 1:
The patent introduces a light extraction layer with nanoparticles as an intermediary component between the top electrode and the circular polarizer. This layer extracts ambient light from the display panel structure, preventing it from reaching the circular polarizer and causing light loss, while still allowing the circular polarizer to function effectively in suppressing reflected ambient light.
Solution Approach 2:
The patent changes the optical parameters of the display panel by incorporating nanoparticles with specific refractive indices (1.7-2.0) and size distributions (5-40 nm) into the light extraction layer. These parameter changes enable the layer to selectively extract ambient light while maintaining the contrast-enhancing function of the circular polarizer.
2Productivity
If lens-type or scattering-type light extraction structures are combined with a circular polarizer, then light extraction efficiency is improved, but the dark field effect is destroyed resulting in gray appearance
Solution Approach 1:
The patent applies local quality by using nanoparticles with specific optical properties (refractive index 1.7-2.0, size 5-40 nm) in the light extraction layer. These nanoparticles are strategically positioned to extract ambient light locally without creating the scattering or lensing effects that would destroy the dark field appearance, thus maintaining both light extraction efficiency and the all-black effect.
3Duration of action of stationary object
If a top-emission panel with high aperture ratio is used to improve lifetime, then external quantum efficiency is improved, but ambient light reflection problem is exacerbated
Solution Approach 1:
The light extraction layer with nanoparticles serves as an intermediary between the high-aperture-ratio top-emission structure and the circular polarizer. It extracts ambient light that would otherwise reflect off the high-aperture panel, preventing the exacerbation of reflection problems while maintaining the lifetime benefits of the top-emission design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively absorbs ambient light, maintaining high contrast and extending the display panel's lifetime by ensuring that the light extraction layer does not interfere with the dark field effect, while improving external quantum efficiency.
Implementation Method 1
the light extraction layer with nanometer-sized particles above the top electrode... effectively absorbs ambient light
Implementation Method 2
at least part of the sub-pixels further include a light extraction layer... significantly improves the external quantum efficiency
Data Source
AI summary
A display panel, including an anti-reflection film and a light-emitting element, the light-emitting element includes a substrate and a plurality of mutually isolated sub-pixels disposed on a surface of the substrate; each of the sub-pixels includes a bottom electrode, a functional layer, and a top electrode which are sequentially stacked; at least a part of the sub-pixels further include a light extraction layer; the light extraction layer is disposed on a surface of the top electrode away from the functional layer; and nanoparticles are disposed in the light extraction layer; and a diameter of the nanoparticles does not exceed 40 nm. The display panel has high contrast, while achieving the effect of improving its lifetime.